This is an update in my continuing coverage of the Proxima Centauri B story. Proxima B remains the closest known, or indeed the closest possible, exoplanet to the sun. Even more interesting, it lies within the habitable zone of its star and could harbor conditions favorable to life including liquid water.

The main development in this story is strong evidence that may lay to rest a decades-old mystery. Up until this point, we weren't certain if Proxima Centauri was gravitationally bound to the nearby Alpha Centauri system. It turns out that it probably is bound and that greatly favors the habitability of Proxima Centauri B.

Proxima Centauri is the closest star to the sun. A small, ancient red dwarf, it lies only 4.25 light years away. This is as close as it gets, and indeed will eventually be within our reach to visit. The planet orbiting it is about the same mass as Earth and may be very similar or could be radically different. We just don't know yet.

Key to this story was determining the star's radial velocity, or how it's moving through space. Using the High Accuracy Radial velocity Planet Searcher instrument in Chile, astronomers have obtained very precise measurements of Proxima Centauri and Alpha Centauri's radial velocity. They match up very well, both stars are moving relative to the sun in the same direction. This strongly suggests that they are gravitationally bound.

That would imply that all three stars that make up the Alpha Centauri system formed within the same nebula billions of years ago along with the exoplanet. They would also all be roughly the same age. The speculative model based on what we know goes that Proxima Centauri was once far closer to the other stars but was ejected out into its current orbit. The planet likely did the same, forming far from the star but migrating to a lower orbit over time.

Given that it formed distantly, it was probably once an ice world if our solar system is any indicator. That implies the presence of water ice, which seems to be common throughout the galaxy. As the planet migrated, that ice would have melted and if it's still there today, it would be in the form of liquid water.

The only other thing we can infer with any confidence about Proxima B is that it may be tidally locked given how close it is to Proxima Centauri. This would lead to an interesting situation where one side of the planet might be quite hot and permanently facing the star while the other side of the world would be frozen and never see the light of day. This would create a ring of habitability on the terminator zones of the planet that divide permanent day and night.

It could be a ring world where the deep red color of its star would dominate the sky along with two very bright, but distant companion stars. Twilight oceans may lap shores not unlike a permanent sunset on an earthly beach. There may even be life, adapted to its dim environment in ways hard to imagine. But, unlike many of the mysteries that I talk about on this channel, this is one that will be answered. It won't take us long to learn more about this world and in the not too distant future we could be walking on those shores, assuming of course that there aren't others already there.

Thanks for listening! I am futurist and science fiction author John Michael Godier currently with a new book coming out. I pulled out all the stops with this one and asked the deepest question I could think of. If the universe is a computer simulation, then who created it? This book is called Supermind and will be available in a matter of weeks, in the meantime be sure to check out my other books at your favorite online retailer and subscribe to my channel for in depth, regular explorations into the interesting, weird and unknown aspects of this amazing universe in which we live.